Realistic Human Skin in Cycles
Here's a shot at what your tree might look like, as corrected by @Jachym.




Introduce the branches one at a time,starting with Diffuse color on its own.
Unlike the illustration, forget the AO branch to begin with. Plug the Diffuse map straight into the Base Color.
Then check the Normal. If you want to get a better view, you can temporarily unplug the Diffuse map to see  the effect on a white object.
When that's OK, plug the Diffuse back in, and go for the Shininess.
Now go for the Subsurface Scattering. Split the Diffuse, and plug it into Subsurface Color too.
Plug the 'M' map into the Subsurface Radius.
Depending on the size of your model, adjust the 'Subsurface' slider down. (I would recommend scaling the model in Edit mode, to life-size, in whatever units your scene is in.) Plugged in as shown, the RGB values in the red 'M' map represent the distances R,G and B are allowed to scatter through the object, in Blender Units, before attenuating to 0. Those distances are then multiplied by the value in the 'Subsurface' slider.


This is hard to check without the file.. but I hope it heads in the right direction.


If you really need the AO, (the lighting shouldn't really need faking..), use an RGB Mix node set to 'Multiply' or 'Overlay' to mix it with the Diffuse map on the way into the Base Color.


There's every chance @Jachym will have to correct me again :)